Method for protecting industrial substrates from fungal or bacterial attack

ABSTRACT

Method for protecting fabrics, plastics, paints, etc. from fungal and/or bacterial attack comprising treating same with N-(2-methyl-1-naphthyl) maleimide.

This is a division, of application Ser. No. 843,610, filed Oct. 19,1977, now U.S. Pat. No. 4,141,905.

DETAILED DESCRIPTION OF THE DISCLOSURE

Synthetic, film-forming materials, such as those used in the manufactureof plastic films and woven fibrics made from synthetic or cellulosicfibers are known to be subject to bacterial or fungal attacks. This isparticularly known to those manufacturers whose products will be used onexterior surfaces and/or under conditions that are prone to hostundesirable fungal and bacterial micro-organisms.

In order to prevent bacterial or fungal attack and consequentdeterioration of the polymeric or cellulosic material so attacked or thesubstrate to which they are applied, manufacturers of plastic films orwoven fabrics have used a number of biocides on a routine basis. Many ofthe currently used industrial biocides are organometallics, such asarsenicals; they are highly successful in preventing bacterial or fungaldeterioration of plastics. For environmental reasons, however,organometallics are now less accepted in some of the industrial useswhere biocides are needed. It has thus become highly desirable to findnew, non-metallic biocides that provide protection for polymericsubstrates of all types, including film-formers, plastics, cellulosics,and the like.

It has now been found that a cellulosic, plastic or film-formingpolymeric composition, knitted, woven, molded or extruded into acontinuous form can be protected against bacterial or fungal attacks bytreating such substrates with the new compound of the current invention:N-(2-methyl-napthyl)maleimide. The new compound is a homolog of acompound in U.S. Pat. No. 2,444,536, but unlike theN-(1-naphthyl)-maleimide described there as a fungicide and insecticide,the current compound, in addition to the expected fungicidal activity,has strong antibacterial properties. Thus, the new compound is a potentand highly useful industrial biocide; it can easily be incorporated intoor applied to the surface of plastics, polymers, cellulosics and similarorganic substrates. At concentrations of 0.005-5.0% by weight, the newcompound will completely protect said substrates against bacteria orfungi often found in the environment. Furthermore, in contrast tocommonly used industrial biocides including arsenicals, the new biocidedoes not lose its activity when exposed to UV-light.

When a substrate is treated with the new compound of this invention,growth of bacteria or fungi also is inhibited in areas in contact withthe surface of said treated substrate, particularly when said compoundis present in the higher range of the concentration recited above.

For the purpose of the present description, the term "film-forming"should be understood to refer to the polymeric particles, whether thoseparticles are present as dry, particulate matter or in liquid,dissolved, suspended, coherent, continuous or any other form,particularly including the ultimate form for which said particles aredesigned. The term "plastic" is used in a similarly broad version and isto be understood to include those polymeric materials which can beextruded, injection- or compression-molded into the desired ultimateshape. The term "cellulosic" is primarily designed to refer to cotton,but also includes those cellulosic derivatives wherein the basiccellulosic structure of the fibrous material has undergone some chemicalmodifications that do not materially change the number of repeatingunits in the cellulose structure.

The current biocide is particularly useful for the treatment of leather,leather substitutes, wood or plastic products, or fabrics made fromcellulosic or olefin polymers, knitted, woven, extruded or molded intostructures exposed to outdoor conditions, such as outdoor-wear, tents,boots, belts, tarpaulins, swimming pool liners and the like. The newbiocide can similarly usefully be employed as an additive to industrialfluids, e.g., cooling water, hydrocarbon fluids, metal cutting fluid; italso can be incorporated for its biocidal effect into cosmetics and, ofcourse, paints of all types, including alkyd, oil-based or latex paints.

In a general embodiment, the compound of the current invention is madeby heating maleic anhydride with about a equimolar amount of2-methyl-1-napthylamine in the presence or absence of 0.2-1.6 liters ofa lower fatty acid per mole of reactants for at least 30 minutes,preferably 1-5 hours. When operating in the absence of a solvent,temperatures of 130°-190° C. are best suited; where a solvent is used,temperatures of between 100° C. and the boiling point of the solventgive best results. Only lower fatty acids, particularly glacial acetic,propionic and butyric acids are suitable as reaction media. Othersolvents only produce the corresponding maleamic acid without ringclosure. After the product crystallizes out upon cooling, thecrystalline mass is collected by filtration, washed with ethanol orwater and dried in vacuo. In the cases where no crystalline productseparates upon cooling, part or all of the acid solvent is removed fromthe reaction solution by vacuum-distillation or evaporation in vacuo.The residue can then be triturated with dilute alcohol or water to givecrystalline N-(2-methyl-1-naphthyl)maleimide. Again, the solid iscollected by filtration, washed with dilute alcohol or water, and driedat 50° C. over P₂ O₅ in vacuo.

Normally, the product obtained in the above manner is pure enough foruse as an industrial biocide. However, if further purification isdesired, the above compound can readily be purified either byrecrystallization or column chromatography. For recrystallization, thefollowing solvents or combination thereof are most suitable: loweralcohols, particularly methanol, ethanol, 2-propanol, aqueous alcohol,ethyl acetate, acetic acid, methylene chloride, chloroform, petroleumether, benzene, toluene, acetone, dimethylformamide, dimethylsulfoxide.For column chromatography, both silica gel and neutral aluminum oxidecan be used with excellent results. The best solvents or solventcombinations for elution are chloroform, methylene chloride, ethylacetate, benzene, toluene, and petroleum ether or compatible mixturesthereof.

The effect of the above new biocide is best understood by reference to ageneral embodiment: To a film-forming mixture containing a syntheticpolymeric material which is to be processed into a continuous phase andcontains the usual ingredients, such as dyes, pigments, plasticizers,preservatives and the like, is added between 0.005 and 5.0% by weight ofN-(2-methyl-1-naphthyl)maleimide and all ingredients are dispersed toform a homogeneous mass. Such a mixture is stable under normal storageconditions; it can be stored for extended periods of time underconditions usually required for such materials. The shaped article madefrom or coated with this mixture is then resistant to fungal orbacterial attack. This is the case whether said article is obtained bycompression-molding, injection-molding, extrusion or whether it is asurface film as obtained by applying a coating formulation throughbrushing, spray-coating or dipcoating onto the substrate and subsequentdrying. These coating methods primarily are applicable where thecontinuous substrate is a woven or knitted cellulosic material or wood.In most instances, the substrate and areas in contact therewith are alsoprotected from deterioration by bacterial or fungal attack.

In order to illustrate the preparation and use ofN-(2-methyl-1-naphthyl)maleimide in connection with a film-forming orplastic mixture or a woven fabric, reference is made to the followingexamples which, however, are not intended to limit the invention in anyrespect.

EXAMPLE 1

A solution of 538 g. of 2-methyl-1-naphthylamine in 700 ml. of glacialacetic acid is placed in a 3-liter, three-necked flask equipped withstirrer, a reflux condenser and thermometer. To this solution is added asolution of 373 g. of maleic anhydride in 500 ml. of glacial acetic acidin a slow stream under vigorous stirring. The mixture is heated atreflux for 3 hours. Upon subsequent cooling to room temperature andoccasional agitation to induce crystallization,N-(2-methyl-1-naphthyl)maleimide crystallizes and is collected byfiltration. The material is sucked almost dry and washed with 95%aqueous ethanol and a large amount of water. It is dried in a vacuumoven at 80°-110° C. for 8 hours, producing 623 g. (76.8%) theory of atechnically pure sample as a light yellow, crystalline powder, meltingat 156°-8° C.

By using larger quantities of glacial acetic acid, essentially the sameresults are obtained at 1-10 hours of heating. However, when the heatingtime is shorter than 1 hour, the yield is reduced.

When the above reaction is carried out in the absence of a solvent attemperatures of 130°-190° C., the reaction mixture solidifies uponcooling and the desired product is purified by recrystallization fromethanol or dilute ethanol.

In both instances, higher reaction temperatures and shorter reactiontimes produce about the same yield as lower temperatures and longerreaction times.

EXAMPLE 2

In tests wherein cotton fabric samples are dip-coated in an aqueoussolution to absorb 0.5% by weight of the new compound, incubating saidsamples in nutrient agar for 24 hours at 37° C. with bacteria pink stainor mixed spores (A. niger, A. flavus, C. globosum and P. funiculosum)for 14 days at 31° C. and 90% humidity, it is shown in Table I, column Athat excellent protection is obtained. In most instances, protection isalso obtained in areas surrounding and directly in contact with thecotton fabrics; also, in many instances, similarly good results areobtained after exposing the samples for 24 hours to UV-light (Column B).

                  TABLE I                                                         ______________________________________                                                       A         B                                                    ______________________________________                                        Staph. aureus   7/NGCA      6/NGCA                                            K. pneumoniae   1/NGCA      0/GCA                                             Pink Stain      7/NS        5/NS                                              Mixed Spores    2/NG        0/NG                                              ______________________________________                                         NG = No growth                                                                CA = Contact area                                                             GCA = Growth in CA                                                            NS = No stain                                                                 Number preceeding above abbreviations denotes the size of the protected       area in mm.                                                              

EXAMPLE 3

Cotton samples containing 0.5% of N-(2-methyl-1-naphthyl)maleimide areplaced horizontally on a 4-inch layer of soil and covered with a 1-inchlayer of loosely packed soil. The soil "sandwiches" are placed in ahumidity chamber for 14 days at 30° C. and 90% relative humidity, andthe fabrics are then inspected visually. The recovered samples, afterthis severe test, are in excellent condition and show no sign ofdegradation.

EXAMPLE 4

Film strips are made from polyvinylchloride, containing the usualplasticizer, color stabilizer, preservative, UV stabilizer and 0.5% byweight of the above compound. They are tested in the usual fashion andafter being exposed up to 300 hours in a Weather-Ometer withintermittent water spray and subsequent inoculation with some of thebacteria or mixed spores mentioned above. The results are given below ina comparison with those of the closest homolog, N-(1-naphthyl)maleimide,and one of the best commercially available biocides,10,10'-oxybisphenoxarsine (marketed as Vinyzene® by Ventron), all at the0.5% load level.

                                      TABLE II                                    __________________________________________________________________________            New Compound        Homolog   Vinyzene                                         0   100  200  300   0   100   0   100  200  300                      __________________________________________________________________________                                                         hrs.                     Staph. aureus                                                                         7/NGCA                                                                             6/NGCA                                                                             6/NGCA                                                                             5/NGCA                                                                             5/NGCA                                                                             4/NGCA                                                                             9/NGCA                                                                             8/NGCA                                                                             5/NGCA                                                                             2/NGCA                   K. pneumonia                                                                          0.5/NGC                                                                            0.5/NGC                                                                            0/NGCA                                                                             0/NGCA                                                                             0.5/NGCA                                                                           0/GCA                                                                              8/NGCA                                                                             7/NGCA                                                                             1/NGCA                                                                             0/NGCA                   Pink Stain                                                                            8/NS 7/NS 7/NS 6/NS 4/NS 6/NS 8/NS 5/NS 3/NS 0/HS                     Mixed Spores                                                                          3/NG 2/NG 1/NG 0.5/NG                                                                             0.5/NS                                                                             0/NG 14/NG                                                                              8/NG 3/NG 0/TRG                    __________________________________________________________________________     TRG = Trace growth                                                            HS = Heavy stain                                                         

It is of particular interest to note that with Gram-negative K.pneumoniae, the current compound is highly effective while its homologN-(1-naphthyl)maleimide fails at 100 hours of UV-exposure. The newcompound also compares very favorably to Vinyzene and excells over thelatter in all challenges after 300 hours of UV-light.

EXAMPLE 5

Wooden tongue depressors are dipped into the vinyl-acrylic paintcompounds made according to the following method.

    ______________________________________                                        Water                 250 parts                                               Anionic surfactant    8 parts                                                 Non-ionic surfactant  2.5 parts                                               Tetrapotassium phosphonate                                                                          1 part                                                  Hydroxyethylcellulose 2.5 parts                                               Ethylene glycol       25 parts                                                Cellulose acetate     15 parts                                                Defoamer              3 parts                                                 Titanium dioxide      175 parts                                               Magnesium silicate    250 parts                                               Biocide               5 lbs./100 gals.                                        ______________________________________                                    

The above ingredients are dispersed for 20 minutes and then blended with400 parts of a vinyl-acrylic emulsion (sold as UCAR by Union Carbide)and 1 part of a defoamer.

After the paint is dried, the painted surface is inoculated with amixture of A. pullulans, P. funiculosum and A. niger, containing 10,000spores/ml of each. The samples are then placed in a mold box for aperiod of 4 weeks at 30° C. and 90% relative humidity. Table III shows acomparison of the paint samples with the current biocide, a control (nobiocide) and a sample containing the same amount of Nopcocide®N-96, acommercially accepted biocide. The ratings are: 0 for no growth onsample, 1 for 0-25% growth, 2 for 25-50% growth, 3 for 50-75% growth and4 for 75-100% growth of spores over the painted surface. The ratingsshown are for the three samples with each paint mixture tested.

                  TABLE III                                                       ______________________________________                                        Sample               Rating                                                   ______________________________________                                        Control              4       4       4                                        N-(2-Methyl-1-naphthyl)maleimide                                                                   0       0.5     0.5                                      Nopcocide®N-96   1       0.5     1                                        ______________________________________                                    

EXAMPLE 6

Exposure panels are prepared by dividing 7"×36" white pine boards intosix 7"×6" sections. Each of the sections is painted with a vinyl acrylicpaint, either containing no biocide (blank) or containing a biocide at aspecific concentration. The vinyl acrylic paints are prepared accordingto the formulation and method as described in Example 5.

The painted panels are dried and exposed in standard fashion in a fieldnear San Juan, Puerto Rico. The conditions and the microbial growth onthe panels are evaluated after exposure for four months. The paintemulsion containing 5 lbs./100 gal. N-(2-methyl-1-naphthyl)maleimideshows a rating of 9, paint with 9 lbs./gal. ofdi(phenylmercury)-dodecenyl succinate shows a rating of 5 and paintscontaining no biocides rates 2 on a scale which assigns 10 to nobacterial or fungal growth and 0 shows complete overgrowth of thepainted panels.

We claim:
 1. The method of protecting a cellulosic, plastic orfilm-forming polymeric composition, knitted, woven, molded or extrudedinto a continuous form, against bacterial or fungal attack upon exposureto an environment containing common bacteria and fungi, comprisingincorporating into said continuous form or coating said composition witha biocidally effective amount of N-(2-methyl-1-naphthyl)maleimide. 2.The method of claim 1 wherein said biocidally effective amount isbetween 0.005 and 5.0% by weight.